Session: 31-06 Fan & Propulsor Design

Paper Number: 151333

A Novel Design Method for Electric Aircraft Propulsors 

The electrification of aircraft propulsion systems has unlocked new architectures and mission profiles previously unattainable with traditional gas turbine engines. However, as the design space for electric propulsors expands, so does the need for efficient, mission-matching design methodologies. This paper introduces a novel design and analysis framework for electric aircraft propulsors, which places fundamental aerodynamics at the core of the design process. The demonstrated method enables the designer to shape the flow as it moves through the propulsor, rather than relying on correlations with geometric parameters.  

Airfoil geometries that match the desired flow field are generated using an inverse-design approach based on a precomputed database of 3,000 airfoil sections. This computationally efficient method reduces the number of input parameters required for fan and propeller blade design. The approach builds on a methodology developed by Clark, adapting it for compressor airfoil sections instead of turbine sections. The toolset covers a wide range of operating conditions, including inlet angles, row velocity ratios, Mach, and Reynolds numbers. Radial basis function networks are trained a priori on this database, allowing designers to retrieve airfoil sections that meet specific aerodynamic requirements without the need for time-consuming simulations. In addition to providing the required geometry, the method also returns performance metrics and predicts the entire blade-to-blade flowfield.  

By specifying flow characteristics rather than geometric characteristics, this method unifies conventional design techniques for compressors, propellers, and fans. It also provides insight into whether propulsor ducting is aerodynamically necessary. This work shows two case studies to demonstrate the method's applicability: one for an open propeller and another for a ducted fan. These case studies demonstrate that this methodology is particularly well-suited for electric propulsors and can be used to accommodate the diversity of mission profiles currently being considered for electric air vehicles. Additionally, this method also empowers designers to work with the true non-dimensional parameters that govern flow behavior within and around the propulsor, offering valuable insights into the proximity of design concepts to various feasibility limits. Finally, thanks to the inverse nature of the geometry creation is will accelerate the time required to develop a given propulsor concept to maturity, a feature that is of primary importance to the electric aircraft industry. 

Presenting Author: Alexander Reaves Whittle Laboratory

Presenting Author Biography: Alexander Reaves is a third year Ph.D. student in the Whittle Laboratory at the University of Cambridge, originally from the Phoenix, Arizona. His work focuses on the design and testing of future electric propulsion systems. In 2024 he was awarded the Sir Michael Marshall Award by the Cambridge Branch of the Royal Aeronautical Society for providing the best lecture to the society from a speaker under 30. After his PhD he is hoping to return to the United States for work.

Authors:

Alexander Reaves Whittle Laboratory
James Taylor Whittle Laboratory
Christopher Clark Whittle Laboratory